If early humans had been vegans we might all still be living in caves, Swedish researchers suggested in an article Thursday.

When a mother eats meat, her breast-fed child’s brain grows faster and she is able to wean the child at an earlier age, allowing her to have more children faster, the article explains. That provided a distinct competitive advantage for early humans when limited resources and a small population made it difficult for them to thrive. “Eating meat enabled the breast-feeding periods and thereby the time between births to be shortened,” said psychologist Elia Psouni of Lund University in Sweden. “This must have had a crucial impact on human evolution.”